Supply of oxygen based on breathing of a human body as a living body is achieved through transportation and exchange by circulating blood. Oxygen taken in by breathing is combined with hemoglobin (Hb) in the blood by gaseous exchange at alveoli. The oxygen taken into the blood is transported to the whole body through arterial blood, and is taken into cells through capillaries.
Since cells of respective parts live using oxygen in the blood, it is desirable to measure the oxygen condition of the cranium, in particular, the cerebral cortex in real time, and check the state of the brain cells constantly during in particular cardiac surgery or cardiac massage due to cardiac arrest.
As a method of measuring the oxygen condition of the cerebral cortex, an oxygen saturation measuring apparatus is known that non-invasively measures oxygen saturation in blood inside a living body using near-infrared light by attaching a pad onto a head of a human body (with reference to Japanese Patent Application Laid-Open Publication No. 2016-000240, for example).
In the aforementioned conventional sensor, one light source and two light detectors are used, information of a deep part of a head of a human body is obtained by subtracting information of a shallow part thereof from the information of the deep part thereof. At that time, a center (line) based on a clearance between the light source and one of the light detectors and a center (line) based on a clearance between the shared light source and the other one of the light detectors are misaligned.
Thus, since the center for the deep part and the center for the shallow part are different in the region passing through the near-infrared light, it is hard to say that accurate information of only the deep part is obtained on the basis of those parts in which arrangements of blood vessels are different in a living body, which raises the problem of low reliability.
It could therefore be helpful to provide an oxygen saturation measuring sensor and an oxygen saturation measuring apparatus capable of improving reliability of information of parts having different depth.